The construction of subsurface structures, such as wells for extracting oil, gas, water, minerals, or other materials, or for other purposes, typically involves substantial data gathering and monitoring. The data-gathering and monitoring may involve data relating to a wide variety of physical conditions and characteristics existing in the subsurface structure. Different types of sensors may be used and some may require placement inside the subsurface structure.
Recent advances in semiconductor technology and in nanotechnology have led to the development of extremely small sensors that are able to penetrate porous rock and other subsurface materials. The extent to which the sensors can penetrate the subsurface material in itself provides useful information about the subsurface material. The sensors may also be configured to measure various environmental variables such as temperature, pressure, pH, shear, salinity, and residence time.
These extremely small sensors may be injected in the subsurface material by pushing the sensors through fissures and cracks in the subsurface material using a fluid, such as water. The fluid containing the sensors is pumped into the subsurface structure. The sensors are pushed into the porous subsurface material and acquire data based on the specific sensor type. When the fluid is flushed out of the subsurface structure, the sensors are extracted from the fluid. The data collected by the sensors would then be read from the sensors.
One problem with injecting the sensors into the subsurface material is that it is difficult to determine the location of the sensors in the subsurface material at the time the data was gathered. There is a need for a way of determining the location of the sensors in the subsurface material as the sensors gather data.